油猴脚本

// ==UserScript==
// @name         Copy Selected Text Button
// @namespace    http://tampermonkey.net/
// @version      3
// @description  Add a copy button to selected text on a webpage to easily copy the selected text to clipboard
// @match        *://*/*
// @exclude      https://www.yihan.it/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    // create a copy button
    var copyBtn = document.createElement('button');
    copyBtn.id = 'copyBtn';
    copyBtn.style.display = 'none';
    copyBtn.style.position = 'fixed';
    copyBtn.style.zIndex = '9999';
    copyBtn.style.top = '0';
    copyBtn.style.right = '0';
    copyBtn.style.margin = '3px';
    copyBtn.style.padding = '5px';
    copyBtn.style.border = 'none';
    copyBtn.style.borderRadius = '3px';
    copyBtn.style.background = '#000';
    copyBtn.style.color = '#fff';
    copyBtn.style.fontSize = '7px';
    copyBtn.style.cursor = 'pointer';
    copyBtn.innerText = '复制';
    copyBtn.style.boxShadow = '2px 2px 5px rgba(0, 0, 0, 0.3)';

    // add copy button to document body
    document.body.appendChild(copyBtn);

    // add event listener to document body
    document.addEventListener('mouseup', function(e) {
        var selection = window.getSelection().toString().trim();
        if (selection !== '' && !e.target.matches('input[type="text"], textarea')) {
            copyBtn.style.display = 'block';
            copyBtn.style.left = e.clientX - copyBtn.offsetWidth + 30 + 'px';
            copyBtn.style.top = e.clientY - copyBtn.offsetHeight + 'px';
            copyBtn.addEventListener('click', function() {
                navigator.clipboard.writeText(selection);
                copyBtn.style.display = 'none';
            });
        } else {
            copyBtn.style.display = 'none';
        }
    });
})();

---

适用于网页控制台

(function() {
    'use strict';

    // create a copy button
    var copyBtn = document.createElement('button');
    copyBtn.id = 'copyBtn';
    copyBtn.style.display = 'none';
    copyBtn.style.position = 'fixed';
    copyBtn.style.zIndex = '9999';
    copyBtn.style.top = '1000';
    copyBtn.style.right = '1000';
    copyBtn.style.margin = '3px';
copyBtn.style.padding = '5px';
copyBtn.style.paddingLeft = '8px';
copyBtn.style.paddingRight = '8px';
    copyBtn.style.border = 'none';
    copyBtn.style.borderRadius = '3px';
    copyBtn.style.background = '#000';
    copyBtn.style.color = '#fff';
    copyBtn.style.fontSize = '7px';
    copyBtn.style.cursor = 'pointer';
    copyBtn.innerText = '复制';
    copyBtn.style.boxShadow = '2px 2px 5px rgba(0, 0, 0, 0.3)';

    // add copy button to document body
    document.body.appendChild(copyBtn);

    // add event listener to document body
    document.body.addEventListener('mouseup', function(e) {
        var selection = window.getSelection().toString().trim();
        if (selection !== '') {
            copyBtn.style.display = 'block';
            copyBtn.style.left = e.clientX - copyBtn.offsetWidth - 10 + 'px';
            copyBtn.style.top = e.clientY - copyBtn.offsetHeight + 'px';
            copyBtn.addEventListener('click', function() {
                navigator.clipboard.writeText(selection);
                copyBtn.style.display = 'none';
            });
        } else {
            copyBtn.style.display = 'none';
        }
    });
})();